Recently, technology relating to electric vehicles (EVs) and hybrid electric vehicles (HEVs) has been rapidly developing. EVs and HEVs are powered, at least in part, by electricity, and these vehicles often collect and store electricity, or in other words, are charged, from off-vehicle sources. As such, various methods of charging EVs and HEVs have been explored. In particular, techniques for wireless charging, or inductive charging, have been the subject of considerable research.
Wireless charging, as opposed to wired charging, improves durability and longevity of the charging components by limiting contact and exposure of the components, increases safety by concealing potentially dangerous wires and connection interfaces, and enhances versatility by allowing charging stations to be implemented in a variety of ways (e.g., as a portable charging pad, embedded in a parking lot or road, etc.). To these ends, wireless charging relies on an electromagnetic field to transfer energy between a charging station (e.g., wireless charging assembly) and an electrical device, such as a smart phone, a laptop, or an electric vehicle, as in the present case. Energy is sent through an inductive coupling formed between the wireless charging assembly and the device. Typically, an induction coil in the wireless charging assembly (i.e., primary coil) uses electricity, often provided from the power grid, to create an alternating electromagnetic field. Parameters of the coil design include the radius, shape, number of turns, and spacing between turns, which are designed for the specific application. An induction coil in the electrical device (i.e., secondary coil) may then receive power from the generated electromagnetic field and convert it back into electrical current to charge its battery. As a result, the primary and secondary induction coils combine to form an electrical transformer, whereby energy can be transferred between the two coils through electromagnetic induction.
Notably, efficient wireless power transfer between the primary and secondary coils depends on proper alignment between the two coils. Misalignment occurs when the primary coil is laterally offset from the secondary coil, resulting in a loss of power transfer efficiency because the incident magnetic flux on the secondary coil is not at the optimal angle. For illustration, FIG. 1 shows an example primary coil conventionally used for wireless power transfer. The primary coil 100 includes multiple turns and allows for current to flow therethrough. Current flowing through the coil 100 creates an electromagnetic field with a magnetic flux 110. A basic primary coil configuration, such as primary coil 100, results in a magnetic flux direction which is straight upwards, as shown in FIG. 1.
However, the angle of the resultant magnetic flux 110 will not allow for optimal power transfer unless a secondary coil is positioned directly above the primary coil 100. As an example, in the case of wirelessly charging an electric vehicle using a charging pad positioned on the ground, or a charging system embedded in the ground, if the vehicle is not properly parked over the charger, the secondary coil installed in the vehicle will be misaligned with the primary coil transferring energy. Therefore, the electric vehicle charge process will be less efficient. While a slight misalignment can decrease charging efficiency, causing wireless charging to take longer than normal, a larger misalignment can prevent wireless charging entirely.